In case of manufacturing a pneumatic tire capable of running at a run-flat state wherein a side portion of the tire is reinforced with a reinforcing rubber layer, a conventional manufacturing method is explained with reference to FIG. 20 showing a diagrammatically section view of a building drum at a state of attaching each member thereto. As shown in FIG. 20(a), an innerliner rubber 92 is attached onto an outer periphery of a first stage cylindrical building drum 81 to render into a cylinder, and thereafter a reinforcing rubber 93 of substantially a crescent-shaped section is attached onto an outer periphery of each axially side portion of the innerliner rubber 92, and then a carcass member 94 having a width wider than that of the innerliner rubber 92 is attached onto outer peripheries of the innerliner rubber 92, the reinforcing rubber 93 and the building drum 81.
As shown in FIG. 20(b), the building drum 81 is expanded outward in a radial direction between a pair of fold bladders 82 to enlarge a size of a whole of the reinforcing rubber 93 and the innerliner rubber 92 and a size of an axially central portion of the carcass member 94, and a bead core 96 is set to a step difference located at a boundary between the axially central portion and axially outer end portion of the carcass member 94 while closely adhering thereto.
Thereafter, the bladder 82 is expanded to turn up the carcass member 94 located outward from the bead core 96 in the axial direction around the bead core 96, while a sidewall rubber is attached onto the outer periphery of the carcass member 94, whereby a green case 98 is built.
Then, as shown in FIG. 21, the green case 98 is taken out from the first stage building drum 81 and mounted onto a second stage building drum 83, and thereafter the green case 98 is deformed into substantially a toroidal form by approaching the bead cores 96 to each other, while a belt-tread band 99 previously formed on another band building drum and comprised of a cylindrically formed belt member and tread rubber is entered onto a radially outside of the green case 98 and the size of the green case 98 is enlarged to build a green tire. Next, the green tire is transported into a vulcanization mold and vulcanized to manufacture a pneumatic tire.
In the conventional method of manufacturing the pneumatic tire, however, there are some problems. As a first problem, in such a conventional tire manufacturing method, each of the axially outer portions of the carcass member 94 is turned around the bead core 96 at the first stage building drum 81, and thereafter the green case 98 is taken out from the first stage building drum 81 and mounted onto the second stage building drum 83 to deform into a toroidal form. In this case, a relative position relationship between each bead core 96 and the second stage building drum 83 scatters at peripheral positions and hence even if the belt-tread band 99 is accurately transferred onto a given position of the second stage building drum 83, a relative position of the belt-tread band 99 to both the bead cores 96 scatters at peripheral positions, which is a cause of lowering the uniformity.
This scattering is caused as follows. That is, when the carcass member is turned around the bead core 96 at the first stage building drum 81, residual stress is produced in a bead portion of the green case 98, so that when the green case 98 is taken out from the first stage building drum 81 while being gripped from outside, the bead portion of the green case 98 is complicatedly deformed by the residual stress and hence the position relationship between the bead core 96 and the outer surface of the bead portion scatters at positions in the peripheral direction. Therefore, when such a green case is mounted onto the second stage building drum 83, the relative position of the bead core 96 to a rim of the second stage building drum 83 holding the bead core 96 by engaging with the outer surface of the bead portion scatters at peripheral positions.
As a second problem, after the reinforcing rubber 93 of substantially the crescent-shaped section is attached onto the outer periphery of the cylindrical innerliner rubber 92 at the first stage building drum, the carcass member 94 is attached onto the outer peripheries of the innerliner rubber 92, the reinforcing rubber 93 and the building drum 81. In this case, however, since the outer peripheral face of the reinforcing rubber 93 is not flat, cord paths of the carcass member 94 to be attached onto this outer peripheral face become unstable, which scatters the relative position relationship between each bead core and the belt-tread band 99 at peripheral positions and is another factor of lowering the uniformity.
As a third problem, when the carcass member 94 is attached onto the outer periphery of the reinforcing rubber 93, a closed space 97 is formed between a central portion of the carcass member 94 sandwiched by both the reinforcing rubbers and a central portion of the innerliner rubber 92, and thereafter the carcass member 94.between both the reinforcing rubbers 93 and the innerliner rubber 92 are laminated with each other. In this case, it is considerably difficult to completely remove a greater amount of air encapsulated in the closed space 97, so that there is a problem that an air remains in a product tire or an extra deformation is caused in the lamination to generate wrinkles in the innerliner rubber 92.
In order to solve the above problems, there is proposed such a method that a first stage building drum 81A, an outer diameter of a central portion of which being larger than diameters of both side end portions as shown in FIG. 22(a) is used to attach the innerliner rubber 92 onto the outer periphery of the central portion and then the reinforcing rubber 93 of substantially the crescent-shaped section is attached along the outer peripheral faces of both the side end portions of the building drum 81A to flatten a face of attaching the carcass member as shown in FIG. 22(b). In this case, however, the size of the innerliner 92 is reduced at both the axially side end portions of the building drum 81A in the attachment of the reinforcing rubber and hence wrinkles are generated.
In the light of the above problems, the invention is made and is to provide a method of manufacturing a tire in which the scattering of the relative position relationship between both bead cores and the belt-tread band at peripheral positions is controlled to improve the uniformity of the tire and to cause no occurrence of wrinkles in the innerliner rubber and air remaining between the carcass member and the innerliner rubber.